This disclosure relates in general to ethernet connections and, more specifically, but not by way of limitation, to media access control (MAC) addresses for ethernet connections.
A point-to-point Ethernet connection is a common configuration today. Where Ethernet is also the physical layer, a cross-over cable is used to connect two Ethernet nodes. In some cases, another physical layer can be used for point-to-point connections, for example, universal serial bus (USB), FireWire™, RS-232, wireless, etc. When a different physical layer is used, it still appears to be Ethernet from above the data link layer.
A point-to-point Ethernet connection uses physical MAC addresses for addressing data, where each end has a MAC address assigned. The common method to assign MAC addresses is to methodically pre-assign the MAC values from a range bought by the vendor. Each node is administratively assigned a unique MAC address prior to use. This address is static, i.e., the same value is used for the lifespan of the device. Each node on an ethernet network should have a unique MAC address for routing of data packets to function properly.
An Ethernet MAC address or hardware ID is a 48 bit value. The MAC address can be generally broken down into two 24 bit fields, namely the vendor and device identifiers. A particular manufacturer may rents a particular vendor identifier, e.g., for a yearly fee. The 24 bit device identifier allows 16,777,216 unique IDs associated with that vendor identifier to be assigned by that manufacturer. As more nodes are shipped, more vendor identifiers are purchased.